A segregated phase comparison relaying system which is arranged to phase compare the current in each of the phase conductors as well as the ground fault current is described and claimed in an application for U.S. Pat. Ser. No 402,687, now allowed, and which has been assigned U.S. Pat. No. 3,893,008 and an issue date of July 1, 1975. As set forth therein, a separate communication channel is provided for each of the transmitted line operating conditions. In accordance with the teachings of this invention, a single channel is used to transmit a time divided multiplexed signal which sequentially contains all of the line operating conditions. The multiplexed signal is decoded at the receiver with a minimum time delay upon the occurrence of a fault. In the illustrated embodiment, a guard word of 6 data bits is continually transmitted in the absence of a fault, from the transmitter location (hereinafter sometimes referred to as the remote location). This guard word contains a synchronizing signal that maintains the 6 data bit counter at the receiver location (hereinafter sometimes referred to as the local location) in exact synchronism with the 6 data bit signal generator at the remote location. As long as the data bits of the guard word are being received, a guard or inhibit signal will be maintained at the local location. The data-bit arrangement of the guard word determines the time of the occurrence of the synchronizing signal at the local location.
When a fault condition is sensed at the remote location, the transmission of the guard word is terminated and the transmission of the proper fault word, which describes the existing fault operating condition, is initiated. The fault words contains three data-bits, each data-bit representing the line conducting condition of a different line conductor as determined by its sensor. The three data-bits for the three separate line conductor sensors are always generated in a predetermined order and exist for the same predetermined time interval. Since the time intervals of the demodulating or decoding network at the receiver are synchronized with the time intervals of the coding network at the transmitter, and the data-bits of the fault words are derived by scanning the outputs of the line sensors in an endless chain or loop, the data-bits from the remote location may be time decoded for determining at the local location the operating condition of the individual line conductors at the remote location.
It should be appreciated from the foregoing that under normal operating conditions, a code word from the transmitter maintains the decoder of the receiver synchronized so that when a fault occurs, the comparison of the operating conditions of the line conductors at the local and remote locations is initiated without delay whereby the proper circuit breakers may be acutated promptly to deenergize the faulted conductor or conductors, as the case may be.